Synthesis, structure, and spatial arrangement of Si-substituted N-(dimethylsilylmethyl)imides

Abstract

The synthesis of N- (chlorodimethylsilylmethyl)succinimide and N-(chlorodimethylsilylmethyl)-glutarimide by the reaction of the corresponding N-trimethylsilylimides with chlorodimethylsilane and by the reaction of unsubstituted imides with a mixture of hexamethyldisilazane with dimethylchloromethylchlorosilane is described. The formation of N-(chlorodimethylsilylmethyl)succinimide is followed by substitution by the silicon atom, which, depending on the reagent ratio, provides N-(dimethylsuccinimidomethyl)succinimide as the major or minor product. 1 H, 13 C, and 29 Si NMR spectroscopy and X-ray diffraction analysis showed that the silicon atom in N-(chlorodimethylsilylmethyl)glutarimide is five-coordinate. By contrast, in N-(chlorodimethylsilylmethyl)succinimide and N-(dimethylsuccinimidomethyl)succinimide, according to NMR and X-ray diffraction data, the silicon atom is four-coordinate. Quantumchemical calculations by the AM1 method show that the molecular conformations of N-(chlorodimethylsilylmethyl)imides containing an intramolecular O6Si bond are not energetically most favorable in the gas phase.One of the lines of our research on specific structural features of (O3Si) chelate compounds of fivecoordinate silicon is elucidation of the effect of substituents on the C and Si atoms on the strength of C=O6Si coordination and activity in substitution reactions at the silicon atom [1]. In the case of ligands containing bidentate lactamomethyl fragments, the strength of O6Si coordination, all conditions being equal, increases in going from five-to six-and sevenmembered lactam derivatives. At the same time, the Si3Cl bond in five-coordinate silicon derivatives is more reactive than in four-coordinate in SNSi reactions [2]. The most important factor that determines the possibility of spontaneous substitution at the trigonal bipyramidal Si atom in reactions with trimethylsilyl derivatives Me 3 SiY is formation of a compound with a stronger O6Si coordination bond [3].It was previously established that the N,N-bis-(acetyl)aminomethyl ligand, like amidomethyl [4] and lactamomethyl [5,6], exhibits chelating ability. Proceeding with this research, we prepared N-chlorodimethylsilyl derivatives of 5-and 6-membered cyclic imides of dicarboxylic acids and studied the effect of the size of the imide ring on the strength of O6Si coordination. The structures of the products in different aggregative states were established by NMR spectroscopy and X-ray diffraction analysis, as well as by quantum-chemical calculations. N-(Chlorodimethylsilylmethyl)amides,-lactams, and imides are most commonly prepared by reactions of their N-trimethylsilyl derivatives with chloro(chloromethyl)dimethylsilane [4,6,7]. Despite the fact that this synthesis involves many stages (initial formation of transsilylation product, followed by O-silylmethylation, and, finally, N-silylmethylation), it usually proceeds very smoothly with practically quantitative yields of N-silylmethyl derivatives [1]. We made use of this method for preparing cyclic N-(chlorodimeth...

Study of Binuclear Silicon Complexes of Diketopiperazine at SN2 Reaction Profile

“…It is evident that the 29 Si NMR signals at room temperature are not an average of the two separate signals that appeared for 3b (Figure 4A) and 3d (Figure 4B) at the lower temperature and that the changes are a result of Si-X bond breaking. [22][23][24][25] If Si-O bond breaking was predominant, we would have observed an average signal of the two separate signals in the 29 Si NMR spectra at lower temperature. At 20 °C the signal due to 3 000 has completely disappeared as a result of rapid exchange between the small residual signal intensity of 3 000 with that of the predominant 3 00 .…”

Pentacoordinate silicon complexes with dynamic motion resembling a pendulum on the SN2 reaction pathway

“…Complex 9 was prepared as previously reported. 28 The compounds 6-9 have been characterized by their 1 H, 13 C and 29 Si NMR spectra and elemental analysis. Most of the compounds were subjected to X-ray crystallographic analysis.…”

“…Following on from the kinetics and mechanistic studies reported by Voronkov, Baukov, and us on the stereodynamic process involved with amides, 1-5, we wish to communicate herein some of our recent results concerning the synthesis and stereodynamic processes involving five different monosubstituted analogous structures (X = F, Cl, Br, OTf, I) of glutarimides, 6a-e, Scheme 1. 4,[25][26][27] In this work, two approaches to avoid the problems associated with the symmetry of the acetylacetamide 1 configuration were pursued. Firstly, the di-amide was locked into a specific geometry arrangement by linking three alkyl groups to form a six-membered ring.…”

“…Selected bond lengths (Å) and angles [°] of 6a, b,26 d, e 7a, 8, and 9 (see Fig.4Afor numbering scheme)…”